Catalytic hydrogenation of aromatic epoxy resins, for example diglycidyl ethers of bisphenol A, produces cycloaliphatic diepoxides. Cycloaliphatic diepoxides are useful for manufacturing weatherable coatings components in coating applications such as marine coatings, protective coatings (for example, storage tanks; bridges; industrial architecture; and the oil and gas segment), and electronic materials applications.
Currently, a few cycloaliphatic epoxy resins are available commercially based on hydrogenated bisphenol A. For example, U.S. Pat. No. 3,781,244 discloses a process for the industrial preparation of aromatics-free epoxy resins as shown in the following chemical reaction scheme, Scheme (I):

The above aromatics-free epoxy resins are commercially available under the trade names of, for example, Epalloy 5000 and Eponex 1510; and these commercial epoxy resins have long been the industry standard for use in manufacturing weatherable coatings.
Coatings made by curing the above known cycloaliphatic epoxy resins exhibit weatherability, chalk resistance and gloss retention. However, the process illustrated in above Scheme (I) produces cycloaliphatic epoxy resins having (1) a high viscosity (for example, greater than [>] 1,300 mPa-s at 25° C.), (2) a high epoxy equivalent weight (EEW) (for example, >210 g/eq), and (3) a high total chlorine content (for example, >2 wt %). And, when a curable coating composition is made from the above known cycloaliphatic epoxy resins, the resultant curable coating composition exhibits low-grade chemical resistance, adhesion and flexibility; or the resultant curable coating composition is unsuitable for certain applications especially the ones pertaining to electronic materials.
Processes for catalytic hydrogenation of bisphenol A diglycidyl ether are disclosed for example in U.S. Pat. Nos. 3,336,241; 4,847,394; 5,530,147; 5,614,646; and 6,130,344; and U.S. Patent Application Publication No. 20040176549. However, the above prior art lacks recipes for producing a high quality cycloaliphatic epoxy resin product, for example, the above known processes do not provide a product having a viscosity lower than 1,300 mPa-s at 25° C., an EEW lower than 210 g/eq, and a chlorine content lower than 1 wt %. For example, U.S. Pat. No. 3,336,241 discloses a process for direct catalytic hydrogenation of bisphenol A diglycidyl ether having an EEW of 170.4 g/eq, in the presence of a rhodium or a ruthenium catalyst, to produce a hydrogenated epoxy resin having an EEW of 256 g/eq as described in Example 1 of U.S. Pat. No. 3,336,241. The EEW of 256 g/eq of the cycloaliphatic epoxy resin product disclosed in U.S. Pat. No. 3,336,241, suggests a retention of only 69 percent (%) epoxy groups upon hydrogenation of bisphenol A diglycidyl ether starting material.
The above prior art process suffer from several disadvantages including for example: (1) the process produces a product with a high viscosity (for example, >1,300 mPa-s at 25° C.) and/or a high chlorine content (for example, >2 wt %); (2) the process involves three steps; (3) the hydrogenated reaction intermediate reacts with epichlorohydrin less selectively than its aromatic precursor, resulting in a large amount of residual chlorine from the formed byproducts.
It would be advantageous in the industry to prepare a hydrogenated epoxy resin composition product with enhanced properties, such as, for example, a product having a viscosity, of for example ≤1,000 mPa-s at 25° C., without having to use diluents or solvents resulting in improved product processability.